1. Field of the Invention
The present invention relates to an automatic screening mechanism used with an optical fiber fusion-splicer in which exposed ends (from which coating are removed) of two optical fibers aligned with each other in an axial direction are butted and two fibers are integrally fused by heating a butted portion, and more particularly, it relates to an automatic screening mechanism for ascertaining strength of a fused portion by pulling the optical fibers in directions opposite to abutting directions after fusion-splice.
2. Related Background Art
In general, an optical fiber fusion-splicer includes a screening mechanism for ascertaining strength (screening) of a fused portion by effecting a tensile test after two optical fibers are fusion-spliced. In recent years, in answer to requirements of compactness and simple construction of the optical fiber fusion-splicer, there has widely been proposed an optical fiber fusion-splicer in which the screening is performed by utilizing driving mechanism for shifting the optical fibers to align two optical fibers with each other and/or to abut tip ends of the optical fibers against each other. An example of such an optical fiber fusion-splicer is shown in FIG. 6.
The optical fiber fusion-splicer shown in FIG. 6 comprises two fiber holders C on which two optical fibers B having exposed tip end portions A (from which coating are removed) for fusion-splice are set, two holder tables D on which the fiber holders C are mounted, a connection table F having V-shaped grooves E into which the tip end portions A of the optical fibers B set on the fiber holders C are fitted, and fiber clamps G for pressing the tip end portions A of the optical fibers B fitted in the V-shaped grooves E from the above, thereby fixing the tip end portions in the grooves. In this machine, the holder tables D are shifted by driving mechanisms (not shown) in directions shown by the arrows a to abut the tip end portions A of the optical fibers B, and, after the butted tip end portions A of the optical fibers B are fitted into the V-shaped grooves E of the connection table F, the fiber clamps G waiting at positions (waiting positions) shown in FIG. 6 are rotated in directions shown by the arrows c to press and fix the tip end portions A in the V-shaped grooves E of the connection table F by means of pressing members K provided on free ends of the fiber clamps G. In this condition, the tip end portions A are fusion-spliced by applying heat, and, thereafter, the fiber clamps G are rotated in directions shown by the arrows d to return them to their waiting positions, and then, the holder tables D are shifted in directions shown by the arrows b to pull the optical fibers B in the same directions. In this way, the screening is effected.
The above-mentioned conventional screening mechanism arose the following problem.
When the screening is effected, it is not required that the tip end portions of the optical fibers are pressed and fixed in the V-shaped grooves by the fiber clamps; to the contrary, if the screening is effected while the tip end portions are being fixed, there arise problems that the optical fibers are damaged and/or, due to excessive force, the optical fibers are broken or connection strength is worsened. To avoid this, it is required that, before the screening is started, the fiber clamps are returned to their waiting positions to release the fixing of the optical fibers. However, in the conventional screening mechanism, initiation of the screening and initiation of the shifting of the holder tables in the directions b are performed manually by the operator, in a condition that the releasing of the fiber clamps is forgotten, the screening may be started. Further, the execution of the screening itself may be forgotten.
An object of the present invention is to provide a screening mechanism for an optical fiber fusion-splicer, in which, when fixing of tip end portions of optical fibers effected by fiber clamps is released, screening is automatically started, there is no danger of effecting the screening while the optical fibers are fixed by the fiber clamps and there is no danger of forgetting the screening.
According to a first aspect of the present invention, there is provided a screening mechanism for an optical fiber fusion-splicer including two holder tables for holding two optical fibers to be fusion-spliced in an opposed relationship, a connection table disposed between the holder tables and having guide grooves into which tip end portions, from which coatings are removed, of the two optical fibers held by the respective holder tables are fitted, and fiber clamps capable of rotating from their waiting positions to positions above the guide grooves and adapted to press the tip end portions of the optical fibers into the guide grooves, the screening mechanism comprising a sensor capable of detecting the fact that the pressing of the tip end portions of the optical fibers effected by the fiber clamps is released, and wherein, when the releasing is detected by the sensor, one or both of the holder tables are automatically shifted in directions opposite to optical fiber abutting directions to pull the optical fibers thereby effect screening.
According to a second aspect of the present invention, two optical fibers to be fusion-spliced are set on two fiber holders independently, and the fiber holders are mounted on the corresponding holder tables.
According to a third aspect of the present invention, the fact that the pressing of the tip end portions of the optical fibers effected by the fiber clamps is released is detected by detecting the fact that the fiber clamps are returned to their waiting positions.